Various display technologies have been developed for different applications. For example, electrophoretic displays (EPDs) are designed for electronic paper applications to mimic an appearance of ordinary ink on paper. An EPD generally includes a plurality of charged particles dispersed in an electrophoretic layer. The charged particles migrate under influence of an electric field to reflect ambient light for displaying images.
Conventionally, EPD panels are monochrome, typically with 16 levels of grayscale. Lately, color EPD panels have been developed by adding color filter array (CFA) over the monochrome EPD panels. These color EPD panels have certain disadvantages in brightness and color saturation, because the CFA passes through only a fraction of visible light and attenuates both incident light and reflected light significantly. Therefore, it is highly desirable to boost the color saturation for EPD color panels.
Because input image data for an EPD color panel are often represented in a red-green-blue (RGB) color space, a conventional approach to enhance color EPD's brightness and color saturation is to boost the RGB values of pixels on an EPD color panel by a certain amount. However, this approach often causes color shifting and results in loss of color fidelity.
There is another conventional approach to enhance brightness and color saturation of EPD color panels. Input image data can be converted from the RGB color space to a hue-saturation-lightness (HSL) color space, the saturation values of the HSL image data may be adjusted, and then the adjusted HSL image data may be converted back to the RGB color space. FIG. 1 illustrates a conventional system 100 for performing saturation adjustment of input color values. A color space converter 102 converts an RGB representation 104 of an input pixel color value 106 into an HSL representation 108 that includes a hue value, a saturation value and a lightness value. A saturation-adjustment component 110 adjusts the saturation value of the HSL representation 108, and outputs a new HSL representation 112. A color space converter 114 converts the new HSL representation 112 into a new RGB representation 116 which is output for providing an adjusted pixel color value 118.